1. Field of the Invention
The present invention relates to a process for treating a yarn in motion, and is more particularly a process for cooling the yarn after it has passed through a heater during a texturing operation, in particular false twist.
It also relates to an installation for implementing this process.
In the rest of the description, the invention will be described as applied to a texturing process called "false twist", according to which process the yarn in motion is subjected to a temporary twist and to a thermal treatment in the twisted state, the yarn being possibly subjected to a fixing treatment.
It is obvious that this does not limit the scope of the invention and that it may also be applied to all processes in which a yarn in motion is thermally treated, the yarn then needing to be cooled rapidly before passing into a treatment unit situated downstream of the thermal treatment unit.
Moreover, the present invention applies to any type of mono- or multifilament yarns, or even a succession of fibres.
2. Description of Related Art
The need to cool the yarn in a false-twist machine between the exit from the heater and the spindle, has been practically demonstrated since the start of the industrial development of this technology, as emerges in particular from French Patent No. 1,076,599.
By virtue of the improvement in the performance of false twist spindles and the increase in the linear speeds of the yarns, which, currently, frequently exceed a thousand meters per :minute (1,000 m/min), it has been necessary not only to increase the length of the heaters so that the yarn receives a sufficient quantity of heat for thermal treatment, but also either to extend, to an approximately proportional degree, the length of the cooling path when the latter is performed in free air, or to provide means allowing an accelerated cooling of the yarn between its exit from the heater and its passage through the false twist spindle.
Amongst the various solutions envisaged, in order to produce such an accelerated cooling, it has been proposed to set the yarn in contact with a cooled surface, or even to wet the yarn, as well as to subject it to the action of a jet of cooled air. This latter solution, i.e. cooling by a jet of air, emerges in particular from French Patent No. 1,168,540 (corresponding to U.S. Pat. No. 3,058,291).
This latter technique of cooling by "a current of cold air" which, in general, consists in passing the yarn inside a tube through which a current of cool air or other gaseous product passes, this current being directed in the opposite direction to the direction of advance of the yarn, although allowing accelerated cooling, has nevertheless never been used industrially, at least to the knowledge of the Applicant, which may be explained by the fact that it is difficult to control the treatment conditions which may vary from one position to another, taking into account that the current of air may disturb the motion of the yarns.